1. Field of the Invention
The present invention relates to a semiconductor device fabricating method, more particularly to a method for forming metal interconnection of semiconductor device.
2. Description of the Prior Art
So far, titanium nitride(TiN) layer has been deposited after the deposition of titanium(Ti) layer to make a good ohmic contact between silicon(Si) and metal layer as well as to form a superior barrier metal layer in forming metal interconnection. The problems of the conventional technique will be described referring to FIG. 1a and FIG. 1b.
As shown in FIG. 1a, after forming an insulating layer 12 on a silicon wafer 11, a contact hole 13 is made in the insulating layer by etching the selected region of insulating layer 12. A Ti layer 14 and a TiN layer 15 are consecutively formed on the overall structure including contact hole 13. Ti layer 14 deposited on a junction 16 reacts with Si to form TiSi.sub.2 layer 17 having low resistivity through successive thermal process, and stable contact resistance can be obtained by the elimination of damaged layer, defect layer, natural oxide layer or the like generated from contact etch.
Also as semiconductor device is highly integrated, ultra shallow junction having a junction depth of 0.1 to 0.15 mm is required. If the conventional method is applied to the ultra shallow junction for the formation of a barrier metal layer, the formation of TiSi.sub.2 layer 17 by the reaction between Ti layer 14 and the Si of junction 16 causes problems. The problems include increase of both leakage current and contact resistance due to excessive consumption of dopants and Si of junction. Therefore, junction breakdown can be induced when TiSi.sub.2 layer 17 is formed with a thickness thicker than the junction depth.
FIG. 1b is a cross sectional view showing such a junction breakdown.
On the other hand, another method of the conventional metal interconnection process employs a TiSi.sub.x (x&gt;2) target to form a barrier metal layer. In this case, relatively stable contact resistance can be obtained since TiSi.sub.2 layer having resistivity less than that of Ti is deposited. However, this method can not eliminate damaged layer, defect layer or natural oxide layer generated from contact etch since the TiSi.sub.2 layer is formed without a reaction with Si of junction. Therefore this method is limited to in device application.